In decontamination systems, such as work spaces contaminated with air borne particles such as asbestos particles during asbestos removal operations, it is desirable to see that no air borne particles, such as asbestos fibers, ever leave the work area. In the past, such as in the Greensboro, N.C. Main Post Office Building removal operation, this has been facilitated by providing overlapping polyethylene sheets between the decontamination area and the work area. Air moves into the work area through the overlapping plastic sheets, however if at any time the negative air pressure that is maintained within the work area is lost, the overlapping sheets preclude ambient air in the work area from passing out of the work area into the decontamination area. While such an arrangement is effective, out of an abundance of caution it may be desirable under some circumstances to guard against a positive pressure situation occurring within the work area (instead of a negative pressure situation). Under such circumstances, it is desirable to see that any air that does exit the work area has been properly filtered.
In order to accomplish the above-stated objective, a HEPA filter is provided in a number of different configurations in an air inlet to the work area, e.g. an inlet through a decontamination area. Any air exiting the work area must pass through the HEPA filter, and therefore the air borne particles, such as asbestos fibers, are removed. Thus the decontamination, or other outside area, is not contaminated with asbestos particles even if a positive pressure should somehow develop in the work area.